This is a 5-year renewal application to support 5 postdoctoral trainees for a broad program in Academic Endocrinology. This program has been in place at the Brigham and Women's Hospital/Harvard Medical School since 1985 and has been highly successful in training physicians and basic scientists, many of whom remain in academic endocrinology. In the last 10 year period, 67% of the 18 trainees completing their training remain in a research career. The faculty combines both the physician-scientists of the Endocrinology Division with those basic scientists on the Harvard Medical School faculty whose research is significantly related to endocrinology. Over the last ten years, these 16 faculty individuals have trained over 300 postdoctoral fellows, over 95% of whom remain in research-related careers, either in academic positions or in industry. The faculty are well-funded, with estimated modified direct costs per annum of over $50 million. The 5 trainees appointed each year will be individuals with MD, PhD, or MD/PhD degrees and they will undertake 3-4 years of an intensive research experience in either basic or clinical investigation. The goal of the program is to provide the trainees with sufficient expertise to apply successfully for mentored research awards, such as K23, K08, or K01 awards, or R01 grants, when indicated. The areas of research interest of the faculty include regulation of energy expenditure, insulin sensitivity, mechanisms of calcium signaling, the role of the iodothyronine deiodinases in controlling differentiation and cell division via local activation and inactivation of thyroid hormone, the process of bone development and its clinical implications, the study of G-protein-coupled receptors, particularly in the hypothalamus, the control of skeletal muscle repair and mechanisms of muscle proteolysis in cachexia and muscle atrophy, the mechanisms of steroid hormone action and the epidemiology of diabetes, obesity, and vitamin D-deficiency disorders. Individuals in this program will also be trained to translate the insights they gain to develop strategies for the treatment and prevention of common endocrinology-based public health problems, including diabetes, obesity and osteoporosis.